Andrew M Brown is the Telegraph's obituaries editor.

Christmas Day is not complete without these delights

Greengages from the village of Estremoz in Portugal, ready to be dried and semi-crystallised to make Elvas plums

I'm thinking of two kinds of preserved plums: Carlsbad and Elvas, one from Bohemia and the other from Portugal, semi-crystallised in sugar and very sought after. Both delicacies are seasonal: they appear around Christmas. Agatha Christie mentions them, in the short story The Adventure of the Christmas Pudding. Or, rather, Mrs Lacey remembers them, talking about Christmases past with Hercule Poirot in the drawing room at her country house, Kings Lacey:

She smiled to herself. "All the same old things, the Christmas tree and the stockings hung up and the oyster soup and the turkey – two turkeys, one boiled and one roast – and the plum pudding with the ring and the bachelor's button and all the rest of it in it. One can't have sixpences nowadays because they're not pure silver any more. But all the old desserts, the Elvas plums and Carlsbad plums and almonds and raisins, and crystallised fruit and ginger. Dear me, I sound like a catalogue from Fortnum and Mason!"

Poirot, who has a sweet tooth, replies: "You arouse my gastronomic juices, Madame." Elvas plums are sugar plums, made from greengages grown in the unique microclimate of the Elvas region of the Alentejo, near the border with Spain. The plums are picked in July, cooked then soaked in sugar syrup for six weeks. They they're washed and dried in the sun before being individually packaged.

They are delicious, sticky, meaty, not at all cloyingly sweet, and bursting with flavour, and they make a good present because as well as tasting good they flatter the recipient slightly. As far as I know you can only get them (at this time of year) from Rainha Santa, the company that was established in 1879 for the production of the Elvas plum, and which now deals in Portuguese preserved fruits and other goodies. Failing that, there's Harrods.

One last one is the wonderful Oxford Book of Parodies, edited by John Gross, just reissued in paperback. Any of these will give untold pleasure on Christmas Day. Munch an Elvas or Carlsbad plum as you read: they're ideally chomped in the late afternoon of Christmas Day, when tiny glimmerings of appetite are starting to make themselves felt again. Merry Christmas.